Many industrial operations require that the pressure in an apparatus should have different values during different operations or operation phases. In many cases, the working cycle of an apparatus, e.g., a press or other apparatus comprising a cylinder and piston or like devices, comprises different phases, one or more of which are active or work phases, while one or more of which are passive or non-work phases. Thus, a piston of a press may have an operating cycle including an active or work stroke and an inactive or return stroke, and different pressures should be obtained in the cylinder, for optimal operation, in the two different strokes. The use of a lower pressure during the non-work phase of the apparatus cycle results, in many cases, in a considerable cost saving. In particular, gas and/or energy consumption may be reduced. In other cases, different operations may require different pressures for optimal efficiency. For instance, an apparatus might require a relatively high pressure to start its operation and then a lower one to maintain the operation over a period of time.
Dual level pressure regulation is effected in the art by providing a separate pressure source or pressure regulator for each desired pressure level. A suitable switch may activate one or the other of said pressure regulators according to the phase of the operating cycle that is taking place.
It is a purpose of this invention to provide a pressure control device which can determine two pressure levels, without requiring two pressure sources or regulators, and permits to control said levels in any desired, even continuous, manner.
It is another purpose of this invention to provide such a pressure control device that is simple, space-saving and free from the danger of malfunctions.
It is a further purpose of this invention to provide a dual pressure level control device that normally determines the higher or the lower of the two pressure levels and correspondingly shifts, when actuated, to the lower or higher level, depending on the chosen embodiment of the invention.
It is a still further purpose of this invention to provide a pressure controlled apparatus, comprising, in combination, a working apparatus of any kind, the operation of which requires the creation and control of a pressure, and a pressure control device according to the invention for carrying out the required pressure control.
Other purposes and advantages of the invention will appear as the description proceeds.